Not Applicable
Not Applicable
1. Field of the Invention
The present invention relates to manual controls for operating hydraulic valves on machinery, and in particular to a xe2x80x9cjoystickxe2x80x9d type control device that operates hydraulic valves that control two functions of a machine.
2. Description of the Related Art
Construction and agricultural equipment have working members which are driven by hydraulic actuators, such as cylinder and piston assemblies, for example. Each cylinder is divided into two internal chambers by the piston and selective application of hydraulic fluid under pressure to either of the chambers produces movement of the piston in a corresponding direction.
Application of hydraulic fluid to the cylinder chambers often is controlled by a spool type valve, such as the one described in U.S. Pat. No. 5,579,642. In this type of hydraulic valve, a manually operable control device is mechanically connected to a control spool which slides within a bore in a valve body. Movement of the spool into various positions controls flow of fluid through two separate paths in the valve. For example in one position pressurized hydraulic fluid is directed along one path from a pump to one of the cylinder chambers and other hydraulic fluid drains through a different path from the other cylinder chamber to a tank. By varying the size of orifices in each path, the rate of fluid flow into the cylinder chambers can be varied, thereby moving the piston at proportionally different speeds.
One type of control device for manually operating hydraulic valves, commonly referred to as a xe2x80x9cjoystickxe2x80x9d, can be pivoted about two orthogonal axes to operate a valve assembly which controls actuators for two functions of a machine. For example, movement about one axis may swing a boom left or right, while movement about the other axis raises or lowers the boom. The joystick is normally biased into a centered position at which the hydraulic valve assembly is in the closed state and actuator movement does not occur. In one common configuration, two valve spools are connected to the joystick, one valve spool for each axis of movement. Considering movement along one axis, when a handle of the joystick is pivoted in one direction from center, one valve spool is operated to produce movement of a first actuator in one direction (e.g. to move the boom leftward). Pivoting the joystick handle in the opposite one direction from center operates the valve spool to move the first actuator in another direction (e.g. to move the boom rightward). Similar bidirectional control of a second actuator occurs when the joystick handle is moved in either direction from center about the second axis to operate the other valve spool. The valve spools or components of the control device are biased by springs which cause the control device to return to the neutral center position upon being released by the operator.
The joystick must convert the pivotal movement about an axis into linear motion that can slide the spool or other type of valve member in a hydraulic valve. Such movement conversion should be smooth. Furthermore, the relationship between pivoting the handle and movement of the valve spool should be linear throughout the entire range of motion,
A control device manually operates two hydraulic valve members which control flow of hydraulic fluid to different functions on a machine. The control device includes a base for attachment to a support. A bracket has a main section from which a first leg and a second leg project, preferably orthogonally from the plane of the main section. A pivot shaft rotationally extends between the first and second legs so that the bracket is able to pivot about a first axis with respect to the pivot shaft. A pivot pin couples the pivot shaft to the base in a manner that enables pivotal movement between the base and the pivot shaft (and the bracket) about a second axis that is orthogonal to the first axis.
A first link is pivotally coupled to the pivot shaft for attachment to one of the hydraulic valve members. A second link is pivotally coupled to the bracket for attachment to the other hydraulic valve member.
Pivoting the bracket about the first axis produces linear movement of the first link and thus operates one of the hydraulic valve members. Pivoting the bracket about the second axis produces linear movement of the second link and thus operates the other hydraulic valve member. The bracket can be pivoted about only one of the axes at a time to operate only one of the valve member and the corresponding machine functions. At other times, the bracket can be pivoted simultaneously about both axes to operate both hydraulic valve members and both of the associated machine functions.